<template>
  <div class="pagination">
    <!-- 当前的页码 -->
    <!-- <h1>{{ startNumAndEndNum }} ---- 当前的页码{{ pageNo }}</h1> -->
    <!-- 上 -->
    <button :disabled="pageNo == 1" @click="$emit('getPageNo', pageNo - 1)">
      上一页
    </button>
    <button
        v-if="startNumAndEndNum.start > 1"
        :class="{ active: pageNo == 1 }"
        @click="$emit('getPageNo', 1)"
    >

    </button>
    <button v-if="startNumAndEndNum.start > 2">···</button>
    <!-- <button>···</button> -->

    <!-- 中间部分 -->
    <button
        v-for="(page, index) in startNumAndEndNum.end"
        v-show="page >= startNumAndEndNum.start"
        :key="index"
        :class="{ active: pageNo == page }"
        @click="$emit('getPageNo', page)"
    >
      {{ page }}
    </button>

    <!-- 下 -->
    <button v-if="startNumAndEndNum.end < totalPage - 1">···</button>
    <button
        v-if="startNumAndEndNum.end < totalPage"
        @click="$emit('getPageNo', totalPage)"
    >
      {{ totalPage }}
    </button>
    <button
        :class="{ active: pageNo == totalPage }"
        :disabled="pageNo == totalPage"
        @click="$emit('getPageNo', pageNo + 1)"
    >
      下一页
    </button>

    <button style="margin-left: 30px">共 {{ total }} 条</button>
    <!-- <h1>{{ startNumAndEndNum }}</h1> -->
  </div>
</template>

<script>
export default {
  //eslint-disable-next-line vue/multi-word-component-names
  name: "Pagination",
  //:pageNo="1" :pageSize="3" :total="91" :continues="5"
  props: ["pageNo", "pageSize", "total", "continues"],
  computed: {
    //总共多少页
    totalPage() {
      return Math.ceil(this.total / this.pageSize);
    },
    //计算出连续的页码的起始数字和结束数字
    startNumAndEndNum() {
      const {continues, pageNo, totalPage} = this;
      // 先定义 起始数字  和 结束数字
      let start = 0,
          end = 0;
      //连续页码数字5[就是至少5页]，如果出现不正常现象【就是不够5页】
      //不正常现象【总页数没有连续页码多】
      if (continues > totalPage) {
        start = 1;
        end = totalPage;
      } else {
        //正常现象【连续页码为5 总页数大于5】
        //起始数字
        start = pageNo - parseInt(continues / 2);
        //结束数字
        end = pageNo + parseInt(continues / 2);
        //把出现不正常的现象【strat数字出现0 | 负数】纠正
        if (start < 1) {
          start = 1;
          end = continues;
        }
        //把出现不正常的现象【end数字出现总页码】纠正
        if (end > totalPage) {
          end = totalPage;
          start = totalPage - continues + 1;
        }
      }
      return {start, end};
    },
  },
};
</script>

<style lang="less" scoped>
.pagination {
  text-align: center;

  button {
    margin: 0 5px;
    background-color: #f4f4f5;
    color: #606266;
    outline: none;
    border-radius: 2px;
    padding: 0 4px;
    vertical-align: top;
    display: inline-block;
    font-size: 13px;
    min-width: 35.5px;
    height: 28px;
    line-height: 28px;
    cursor: pointer;
    box-sizing: border-box;
    text-align: center;
    border: 0;

    &[disabled] {
      color: #c0c4cc;
      cursor: not-allowed;
    }

    &.active {
      cursor: not-allowed;
      background-color: #409eff;
      color: #fff;
    }
  }
}

.active {
  background: skyblue
}
</style>
